JP2000331889A - Manufacture of solid-state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-reliability solid-state capacitor by which leakage current characteristics are improved. SOLUTION: With respect to the method for manufacturing a solid-state electrolytic capacitor 15 by which an oxide film 5 is formed on a sintered compact 1 formed of valve action metal, a capacitor device 10 is formed by stacking a conductive polymer layer 6 and a cathode layer 9 in sequence on the oxide film 5, an encapsulation 14 of resin is formed on the capacitor device 10 and then is subjected to aging, the aging is performed by applying a voltage 1.5-2.0 times the rated voltage in a high-temperature atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor having a layer made of a conductive polymer such as polyaniline or polypyrrole.

[0002]

2. Description of the Related Art A solid electrolytic capacitor such as a tantalum solid electrolytic capacitor is manufactured by, for example, the following method. That is, first, one end of an anode lead wire made of a valve metal such as tantalum is buried in advance, and powder obtained by mixing a binder with a fine powder of a valve metal such as tantalum or aluminum is press-molded. After molding, it is heated at a high temperature in a vacuum and sintered to form a sintered body. Next, the sintered body is immersed in a chemical conversion solution and subjected to a chemical conversion treatment to form an oxide film. After forming the oxide film, a manganese dioxide layer or a layer made of a conductive polymer such as polypyrrole or polyaniline is formed. Thereafter, a carbon layer and a silver layer are sequentially formed to form a cathode layer. Then, the anode terminal is connected to the anode lead wire, and the cathode terminal is connected to the silver layer. Further, the capacitor element after the formation of the silver layer and a part of the anode terminal and the cathode terminal are covered with an exterior made of insulating resin or the like. After forming the exterior, aging treatment is performed in a high temperature atmosphere.
By the way, a solid electrolytic capacitor having a layer made of a conductive polymer such as polypyrrole has a characteristic that the equivalent series resistance and impedance are low because a substance such as polypyrrole has high conductivity.

[0003]

However, in a solid electrolytic capacitor having a layer made of a conductive polymer, the resin shrinks when forming an outer package made of the resin. There is a drawback that stress is applied and leakage current tends to increase.

An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor which improves the above drawbacks, improves the leakage current characteristics, and has high reliability.

[0005]

According to the present invention, an oxide film is formed on a sintered body made of a valve metal, and a conductive polymer layer and a cathode layer are formed on the oxide film. In a method for manufacturing a solid electrolytic capacitor in which an exterior made of a resin is formed on a capacitor element that is sequentially laminated and then subjected to aging treatment, a rated voltage of 1.5% is applied in a high-temperature atmosphere.
Aging is performed by applying a voltage of up to 2.0 times.

That is, according to the present invention, by applying a voltage 1.5 to 2.0 times the rated voltage in an atmosphere of high temperature and performing aging treatment, the leakage current characteristics can be improved and the reliability can be improved. Can be improved. If the applied voltage is lower than 1.5 times or higher than 2.0 times the rated voltage, the effect of improving the leakage current characteristics is reduced or the impedance is increased.

[0007]

Embodiments of the present invention will be described below. First, a binder obtained by dissolving camphor, an acrylic resin, or the like in an organic solvent is added to and mixed with fine powder of a valve metal such as tantalum, aluminum, or niobium. After mixing, the mixture is heated to remove the organic solvent by volatilization. Next, the fine powder of the valve action metal is compression molded by a press or the like into a square or cylindrical shape with the anode lead wire made of a valve action metal such as tantalum pulled out. After the compression molding, sintering is performed by heating at a high temperature of about 1800 to 2200 ° C. for about 15 to 60 minutes in an atmosphere such as a vacuum to form a sintered body 1 as shown in FIG. During this sintering, impurities in the powder are also evaporated.

After sintering, a disk-shaped insulating plate 3 made of Teflon, silicone rubber, silicone resin, or the like is arranged at the root of the anode lead wire 2. The insulating plate 3 has a thickness of, for example, less than 0.2 mm, preferably about 0.1 mm. That is, the smaller the thickness of the insulating plate 3, the larger the size of the sintered body without changing the size of the whole capacitor, the larger the capacity, and the smaller the capacity when the capacity is fixed. .

Then, as shown in FIG.
Of the anode lead wire 2 pulled out from the metal plate 4 is welded to a metal plate 4 such as aluminum or stainless steel. Metal plate 4
, A plurality of sintered bodies 1 are attached in order to improve work efficiency.
In this state, the sintered body 1 is immersed in a chemical conversion solution such as nitric acid or phosphoric acid to a predetermined level by visual observation or the like.
A direct current voltage corresponding to the rated voltage is applied to this for chemical conversion treatment. By this chemical conversion treatment, an oxide film was formed at a rate of about 16 ° / V, and finally, as shown in FIG.
An oxide film 5 of about 0 to 6000 ° is formed.

After forming the oxide film 5, a conductive polymer layer 6 is formed on the surface thereof as shown in FIG. The conductive polymer layer 6 is formed, for example, as follows. That is, in the first method, first, the sintered body 1 is impregnated with a solution in which an oxidizing agent or a mixture of an oxidizing agent and a substance to which a dopant made of an acid compound or a salt compound is added is dissolved in an appropriate solvent. Thereafter, when a solution of an oxidizing agent is used, a solution comprising a mixture of a monomer and a substance to which a dopant comprising an acid compound or a salt compound is added is impregnated, the monomer is subjected to a chemical oxidative polymerization reaction, and the dopant is bound. To impart conductivity.
When a mixed solution of an oxidizing agent and a substance such as an acid compound is used, the monomer is impregnated with either a monomer or a mixed solution of the monomer and a substance to which a dopant of an acid compound or a salt compound is added, and the monomer is impregnated with the monomer. A chemical oxidative polymerization reaction is performed to combine the dopants to impart conductivity. These impregnation processes are repeated a predetermined number of times to obtain a predetermined thickness. Thereafter, a drying treatment is performed. In the second method, the sintered body 1 is first impregnated with a solution of a monomer or a mixture of the monomer and an acid compound or a salt compound. Thereafter, when a monomer solution is used, a solution of a mixture of an oxidizing agent and a substance to which an acid compound or a salt compound is added is impregnated to cause a chemical oxidative polymerization reaction and to impart conductivity. When a mixed solution of a monomer and an acid compound is used, an oxidizing agent or a mixed solution of an oxidizing agent and an acid compound is impregnated, and the monomer is subjected to a chemical oxidative polymerization reaction to impart conductivity. These impregnation processes are repeated a predetermined number of times to obtain a predetermined thickness. Thereafter, a drying treatment is performed. Further, a third method comprises the use of monomers,
The sintered body 1 is impregnated with a solution obtained by dissolving a mixture of a substance imparting dopants of an acid compound or a salt compound and an oxidizing agent in a suitable solvent, and a monomer is subjected to a chemical oxidative polymerization reaction to impart conductivity. This impregnation process is repeated a predetermined number of times to obtain a predetermined thickness. Thereafter, a drying treatment is performed.

The oxidizing agent is, for example, potassium dichromate, sodium dichromate, ammonium peroxodisulfate, hydrogen peroxide, ferric chloride, potassium permanganate,
Using manganese dioxide, lead dioxide, etc., 0.1-1.0mo
Make the concentration about l / l.

As the acid compound used as a substance for imparting a dopant, a sulfonic acid compound, a carboxylic acid compound, a phosphoric acid compound and the like are used. In particular, as the sulfonic acid compound, a substance having a dissociation constant substantially equal to or smaller than that of naphthalenesulfonic acid or a derivative thereof and an anion of a dopant smaller than that of naphthalenesulfonic acid or a derivative thereof is used. Examples of such sulfonic acid compounds include, for example, sulfone isophthalic acid and sulfosuccinic acid, methanesulfonic acid, phenolsulfonic acid, sulfosalicylic acid, benzenesulfonic acid, benzenedisulfonic acid, alkylbenzenesulfonic acid and derivatives thereof, camphorsulfonic acid, and sulfoneacetic acid. An acid such as diphenolsulfonic acid is used. The concentration of this acid compound is 0.05 to
Adjust to about 1.0 mol / l. In addition, as the salt compound used as the substance imparting the dopant, an ammonium salt, a sodium salt, or a potassium salt of the above-mentioned acid compound is used. That is, in the case of a sulfonic acid compound, ammonium sulfoisophthalate, ammonium sulfosuccinate, ammonium methanesulfonate, ammonium phenolsulfonate, ammonium sulfosalicylate, ammonium benzenesulfonate, ammonium benzenedisulfonate, ammonium benzenedisulfonate, and ammonium alkylbenzene sulfonate are used as aluminum salts. And its derivatives, and salts such as ammonium camphorsulfonate, ammonium sulfone acetate, and ammonium diphenolsulfonate. Examples of the sodium salt include sodium sulfoisophthalate, sodium sulfosuccinate, sodium methanesulfonate, sodium phenolsulfonate, sodium sulfosalicylate, sodium benzenesulfonate, sodium benzenedisulfonate, sodium alkylbenzenesulfonate and derivatives thereof, and camphorsulfonic acid. Salts such as sodium, sodium sulfone acetate and sodium diphenol sulfonate are used. Further, potassium salts include potassium sulfoisophthalate, potassium sulfosuccinate, potassium methanesulfonate, potassium phenolsulfonate, potassium sulfosalicylate, potassium benzenesulfonate, potassium benzenedisulfonate, potassium alkylbenzenesulfonate and derivatives thereof, camphorsulfone Salts such as potassium acid, potassium sulfonate, sulfoaniline and potassium diphenolsulfonate are used. The concentration of these ammonium salt, sodium salt, and potassium salt compounds is 0.05 to
Adjust to about 1.0 mol / l. Further, in order to increase the solubility of the salt compound and lower the concentration in the solution, hydrochloric acid, sulfuric acid or the like may be added.

Further, as the monomer, for example, acetylene, paraphenylene, pyrrole, vinylene, phenylene, aniline, thiophene, imidazole, thiazole, furan or the like is used, and the concentration is about 0.1 to 1.0 mol / l.

Next, as shown in FIG. 1E, a graphite solution is applied to the surface of the conductive polymer layer 6 to form a graphite layer 7. After the formation of the graphite layer 7, FIG.
As shown in FIG. 5, a silver paste is applied to the surface to form a silver layer 8, which is combined with the graphite layer 7 to form a cathode layer 9, thereby forming a capacitor element 10. After forming the silver layer 8, FIG.
(G) conductive adhesive 1 such as silver conductive paste
1, the lead frame-shaped cathode terminal 12 is connected to the silver layer 8, and the anode lead wire 2 is connected to the lead frame-shaped anode terminal 13. Then, as shown in FIG. 1H, an exterior 14 made of resin is formed by a resin molding method, a resin dipping method, or the like.

After forming the exterior 12, a high temperature (for example, 85 ° C.)
Aging treatment is performed by applying a voltage 1.5 to 2.0 times the rated voltage in the atmosphere described above. The temperature is 8
The temperature is preferably from 5 to 125 ° C, particularly preferably from 85 to 105 ° C.

Then, as shown in FIG.
Then, the anode terminal 13 is formed to manufacture the solid electrolytic capacitor 15.

[0017]

Next, embodiments of the present invention will be described. Example 1 First, powder obtained by mixing a binder with fine tantalum powder is press-compressed into a square shape. At this time, one end of a tantalum anode lead wire is inserted into the powder, and the other end is drawn out. After compression molding, it is sintered in a vacuum to form a sintered body of 1.62 mm × 3.25 mm × 3.80 mm square. Next, the sintered body is immersed in a nitric acid solution and subjected to a chemical conversion treatment at a chemical conversion voltage of 25 V to form an oxide film thereon. After forming the oxide film, a conductive polymer layer made of polyaniline is formed on the surface of the oxide film by a chemical oxidation polymerization method. At this time, it is necessary to fill the inside of the sintered body with polyaniline and to laminate the conductive polymer layer to a predetermined thickness also on the outer peripheral portion, so that the chemical oxidation polymerization treatment is repeated. After forming the conductive polymer layer, it is immersed in a graphite solution to form a graphite layer. After forming the graphite layer, a silver paste is applied to form a silver layer. After the silver layer is formed, the silver layer is connected to the cathode terminal of the lead frame with silver paste, and the anode lead wire is connected to the anode terminal of the lead frame by resistance welding. Thereafter, an exterior made of epoxy resin is formed by a transfer molding method. After forming the exterior, a part of the lead frame is cut. After the cutting, an aging treatment is performed by continuously applying a voltage of 11 V in an atmosphere at a temperature of 85 ° C. for 6 hours. After the aging treatment, the rest of the lead frame is cut, and the cathode terminal and the anode terminal are formed.
A 3 V, 150 μF tantalum chip type solid electrolytic capacitor is manufactured. In this case, the applied voltage during the aging process is approximately 1.75 times the rated voltage.

Example 2: In Example 1, the formation voltage was 16 V, the voltage during the aging treatment was 8 V, and the rating was 4
V, 220 μF, except for the same conditions. In this case, the voltage during the aging process is twice the rated voltage.

Example 3 The same conditions as in Example 1 were used except that the formation voltage was 36 V, the voltage during the aging treatment was 15 V, and the rating was 10 V and 100 μF. In this case, the voltage during the aging process is 1.5 times the rated voltage.

The leakage current was measured for the tantalum solid electrolytic capacitor manufactured by the method of Example 1 and the tantalum solid electrolytic capacitor manufactured by the method of the comparative example, and the equivalent series resistance was measured for a part of the capacitors. 1
Shown in

In the comparative example, the same conditions as in Example 1 were used except that the temperature and voltage during the aging treatment were as shown in Table 1.

The leakage current is a value 5 seconds after the application of the rated voltage. Then, the leakage current before the formation of the sheath and the leakage current before the aging treatment after the formation of the sheath were measured.
And the average value of Comparative Examples 1 to 6 was shown. The equivalent series resistance is a value at 100 kHz.

[0023]

[Table 1]

As is clear from Table 1, the leakage current after the aging treatment is 28 μA (average value) in Example 1, whereas it is 34 to 98 μA (average value) in Comparative Examples 1 to 6. . That is, the former has a size of about 29 to 82% of the latter, and its leakage current characteristics are improved.

For Example 1, a high-temperature load test was performed together with the conventional example, and the number of short-circuit defects was measured.

The conventional example is manufactured as follows. That is, first, powder obtained by mixing a binder with fine tantalum powder is press-compressed into a square shape. At this time, one end of a tantalum anode lead wire is inserted into the powder, and the other end is drawn out. After compression molding, it is sintered in a vacuum to form a sintered body of 1.72 mm × 3.35 mm × 4.20 mm square. Next, the sintered body is immersed in a nitric acid solution and subjected to a chemical conversion treatment at a chemical conversion voltage of 30 V to form an oxide film thereon.
After forming the oxide film, a manganese dioxide layer, a graphite layer, and a silver layer are sequentially formed. After the silver layer is formed, the silver layer is connected to the cathode terminal of the lead frame with silver paste, and the anode lead wire is connected to the anode terminal of the lead frame by resistance welding. Thereafter, an exterior made of epoxy resin is formed by a transfer molding method. After forming the exterior, a part of the lead frame is cut. After cutting,
Aging treatment is performed by continuously applying a voltage of 11 V in an atmosphere at a temperature of 85 ° C. for 18 hours. After aging treatment,
The rest of the lead frame is cut, and the cathode terminal and the anode terminal are formed to produce a tantalum chip type solid electrolytic capacitor rated at 10 V and 150 μF. In this case, the applied voltage during the aging process is about 1.1 times the rated voltage.

In the high temperature load test, the temperature was 125 ° C.
The applied voltage is rated voltage × 1.45, and the test time is 1000 hours. The number of samples is 25 each.

[0028]

[Table 2]

As is clear from Table 2, Example 1
As compared with the conventional example, the leakage current characteristics are excellent, short-circuit is less likely to occur, and the life is longer.

[0030]

As described above, according to the production method of the present invention, an oxide film is formed on a sintered body made of a valve metal powder, and a conductive polymer layer and a cathode layer are sequentially laminated on the oxide film. In a method for manufacturing a solid electrolytic capacitor in which an exterior made of resin is formed on a capacitor element that has been subjected to aging treatment, a rated voltage of 1.5 to 2.
Since a voltage of 0 times is applied, a solid electrolytic capacitor that can improve leakage current characteristics, reduce short circuit defects, and improve reliability can be obtained.

[Brief description of the drawings]

FIG. 1 shows a process chart of an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sintered body, 5 ... Oxide film, 6 ... Conductive polymer layer, 7 ...
Graphite layer, 8: silver layer, 9: cathode layer, 10: capacitor element, 14: exterior, 15: solid electrolytic capacitor. Reference number P2510

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinji Sano 16th Ohira, Okuma, Miharu-cho, Tamura-gun, Fukushima Prefecture Inside Miharu Plant, Hitachi AIC Co., Ltd. 16 characters Ohira Hitachi FIC Co., Ltd. Miharu factory F term (reference) 5E082 AB09 BC14 BC36 LL23 MM27 PP01

Claims (1)

[Claims] An oxide film is formed on a sintered body made of a valve action metal, and an exterior made of a resin is formed on a capacitor element in which a conductive polymer layer and a cathode layer are sequentially laminated on the oxide film.
Then, in a method of manufacturing a solid electrolytic capacitor subjected to aging treatment, the rated voltage of 1.5 to
A method for manufacturing a solid electrolytic capacitor, characterized in that aging is performed by applying a voltage of 2.0 times.